Why does nuclear fusion occur in stars?

Answer 1

The intense gravitational pressure as you near the center of a star is enough to overcome the normal repulsion of two hydrogen atoms for each other, and fuse them. When two hydrogen atoms fuse, they create an atom of helium and release a large amount of energy -- which is why the sun "shines."

Answer 2

The nuclei of all atoms are positively charged and repel each other especially if forced to be close together. The nuclei must be forced to combine against a powerful resistance (repulsion). It takes a great deal of energy to force the fusion which then releases more energy than required to cause the fusion. At the center of the sun (and stars) there is tremendous pressure forcing hydrogen atoms to be very close. There is also tremendous heat causing the hydrogen atoms to bounce off each other with great force. A relatively small proportion of hydrogen atoms obtain just enough energy under pressure to fuse. When the hydrogen fuel of a star is used up the dwindling heat generated is not enough to withstand the great pressure and the star (if massive enough) collapses with no place to go but toward the center. This train wreck results in unimaginable heat and pressure that permits other heavier atoms to be formed by fusion during a supernova implosion/explosion. Our sun is not massive enough to react this way (lucky for us!).

Answer 3

Nuclear fusion, the process by which multiple nuclei join together to form a heavier nucleus, only occurs if tremendous energy 'forces' the nuclei to merge together. These conditions are met in active stars.

A substantial energy barrier must be overcome before fusion can occur. At large distances two naked nuclei repel one another because of the repulsive electrostatic force between their positively charged protons. If two nuclei can be brought close enough together, however, the electrostatic barrier can be overcome by the strong nuclear force which is stronger at close distances than the electrostatic repulsion.

Answer 4

No one knows.